We have a .Net Core 3.1 application which is using EF Core to connect wit the SQL Server database. We are facing one problem, that when an exception occurs in our method due to some reason, for example, a field is mandatory in DB and on SaveChanges, Exception is raised, because the value for that field was passed as null, then next time, when the same method is called with different parameters (even with all correct/mandatory fields), still the old query gets executed in EF Core (I checked this in Output window). Which is very weird and strange behavior.
If we close the application (in debug environment) after the first exception and re run the application with correct payload next time, then everything works fine. May be the EF Core is retrying the earlier failed query again for some reason? or why is this behavior occurring?
Depending on how are you getting messages from the queue, the message may come back to the queue if it is not acknowledge after a while.
With Auto Acknowledge the message will is removed permanently. If you ack after persist in the database, any exception will avoid the ack, so the message goes back to the queue.
I just figured out that the RabbitMQ consumer classes were not properly setup in the Dependency Configuration file. Basically the repository cases were instantiated as static members in the Dependency Config and when Consumers were setup for RabbitMQ, they were passed in these static Repository objects. I removed these static objects, and made use of the Scoped instances of the repository. this resolved my issue.
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This is one of the most bizarre problems I've come across since I started using OData for my mobile apps. The OData server I've developed is backed by SQL Express 2008 and this combination has been installed on 50 different servers and/or PCs over the last 15 months. All 50 servers have been running stable with consistent function for large amounts of data.
A couple of days ago one of my clients contacted me indicating that my client app (running on iOS7) was having an odd error come up when POSTing data to their server. The error had an HTTP code of 400 and the error text is "The operation couldn't be completed. (Timeout error 400.)". My first question is: why is a timeout error coming back with a 400 code? Generally when I get timeouts (due to firewall, etc) they're in the 100x range. There is no indication in the event logs on the server of ANY problems occurring. My own logs (stored in the SQL database) show no error (which is odd because I'm using the generic exception catching method in my OData service to log any problems). I haven't got to the step of adding logging of all requests as yet.
The error is only being raised when posting one particular set of data. All other posts from the device are functioning perfectly. I got the client to re-install the app (deleting all data) and then to download the data set that was causing the error. The download worked fine. We began making changes to the data to replicate what the data looked like when the error occurred in incremental changes, posting the change to the server and observing the result. Most of the incremental changes work fine but certain combinations cause the error to occur. One of the increments involves a large volume of changes and that posts fine, but subsequent alteration of any of the objects (sometimes altering as little as 6 characters in a text field) cause the error to occur. And yet in some circumstances altering objects that have already been posted to the server works without a problem.
I wiped the service components from the server and undertook a fresh install. I shifted TCP ports in case 443 had another listener causing problems. I reset the server. None of these change the behaviour of the error.
My last ditch solution is to completely re-install IIS and .NET Framework but I'd obviously like to avoid this as it's not my server... The server is overseas from my current location so debugging isn't really an option. Hoping someone has an idea as to what I can do diagnostically to try and determine the source of this bizarre 'gremlin'.
Have you tried a more thorough traffic analysis using a tool like Fiddler? The "timeout" error does indeed seem odd and what stood from you post was that your server was "overseas". Could there be something with the "times" that are being used/generated, e.g. server time, local time, etc?
Just to confirm, the "same" exact set of data always fails? Can you replicate this via a remote debugger or via localhost? If so, can you turn on "verbose errors"?
I had converted some tasks to run on a dynamic backend.
The tasks are failing silently [no logged error, no retry, nothing] ~20% of the time (min:10%, max:60%, sample:large, long term). Switching the task away from the backend restores retries and gets the failure rate back to ~0%.
Any ideas?
Converting it to a backend exacerbated the problem but wasn't the problem.
I had specified a task_retry_limit and the queue was a push queue. With a backend the number of instances is specified. (I believe you can replicate this issue on the frontend by ramping up requests rapidly, to a big number).
Tasks were failing 503: Instance Unavailable until they hit the task_retry_limit. This is visible temporarily in Task Queues, but will not show up in Logs.
I should be using pull queues. Even if my use case was stupid I'd probably +1 a task dying due to multiple 503: Instance Unavailable logging something so it doesn't appear like a phantom task.
Which runtime are you using on the backend?
Try running the backend for a bit without dynamic set to true and exercise the failing component.
On my project, I have seen tasks that target a static backend disappear on occasion, but no where near the rate you are seeing.
So, I have a duplex server housed in a service that provides webservices to a Silverlight 4 control. Most of the time everything works -- but one specific callback which should retrieve a collection, never seems to be consumed by the client. I can step through the server code and see the issuance of the response, and, if I watch in Fiddler, I can see my data sent in a transmission that's identical to those that work. On the client, however, my break point for the event handler is just never tripped -- I've verified to the last point I can in the client that the callback is still set.
What I can do to debug further?
EDIT
I figure I should also specify that I'm not seeing any first chance exceptions generated in the output window in visual studio on the client or the server that might be getting handled, and hiding the error.
Are you having this issue?
http://blogs.msdn.com/b/silverlightws/archive/2010/12/15/pollingduplex-using-multiplemessagesperpoll-issue-in-latest-sl4-gdrs.aspx
I've implemented a messaging system over SQL Server Service Broker. It is working great, with the sole exception that every once in a while (maybe once per week per server) my initiator service just vanishes without a trace. The corresponding queue is still there, but the service is missing.
Obviously this causes problems in my system. It's a simple matter to recreate the service by hand, but I'm confused as to what might cause this behavior. I understand that automatic poison message handling causes queues to be disabled, but I don't see anything that indicates services can be disabled or deleted automatically.
When this happens, I usually have a large backlog of messages in multiple application queues, but nothing extreme. Total message backlog is around 200,000.
Does anyone know what might be happening here?
You must have a bug of some sort that issues a DROP SERVICE statement. That is the only way a service gets deleted.
Check the default trace, the DROP statement gets traced and saved into it so you can track down the application/user/statement that issues the DROP. Check sys.traces to find the location of the default trace then open the .TRC file in Profiler.
We are using ASP.NET MVC with LINQ to SQL. We added some features and tested them all to perfection on our QA box. We are using Windows Server 2003 and SQL Server 2005. So when we pushed out changes to the Live web server we also used Red Gate SQL Compare to push new database changes to the LIVE database. We tested again between the few of us, no problems. Time for bed.
The morning comes and users are starting to hit the app, and BOOM. We have no idea why this would happen as we have not been doing any new types of code things that we were not doing before. However we did notice that during the SQL Compare sync the names of all the foreign keys were different between the two databases, not the IDs in the tables, FK_AssetAsset_A0EB67 to FK_AssetAsset_B67EF8 (for example, don't remember the exact number of trailing mixed characters during the SQL Compare), we are not sure why but that is another variable in this problem.
Strangely once this was all pushed out we could then replicate the errors on QA, but not before everything was pushed to LIVE.
QA and LIVE databases are on the same SQL Server, but the apps are on different instances of Windows Server 2003.
Errors generated:
Index was outside the bounds of the array.
Invalid attempt to call FieldCount when reader is closed.
Server failed to resume the transaction.
There is already an open DataReader associated with this Command which must be closed first.
A transport-level error has occurred when sending the request to the server.
A transport-level error has occurred when receiving results from the server.
Invalid attempt to call Read when reader is closed.
Invalid attempt to call MetaData when reader is closed.
Count must be positive and count must refer to a location within the string/array/collection. Parameter name: count
ExecuteReader requires an open and available Connection. The connection's current state is connecting.
Any one have any idea what the heck could have happened?
EDIT: Since we were able to replicate the errors all of a sudden on QA, it might not be a user load issue... Needless to say we all feel really screwed here.
Concurrency always brings bugs out of the woodwork. I'd recommend you check for objects that could be shared among requests (such as static members and singletons) and refactor your code so that as little as possible is shared.
As far as specifics go, for the error "There is already an open DataReader associated with this Command which must be closed first," you may want to try adding MultipleActiveResultSets=True to your connection strings.
It sounds like you're crossing the streams a bit and trying to share DataContexts across requests. My suggestion would be to wire in a dependancy injection framework that creates a new instance of the dependancy for each request.
I use Castle's IoC and wire it into the controller factory so that when it sees a dependancy on a repository it creates a new instance of that repository for each request. If you go this route let me know and I can shoot you a few more resources.